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Dielectric spectroscopy of ionic microgel suspensions

Mohanty, P. S. LU ; Nöjd, S. LU ; Bergman, M. J. LU ; Nägele, Gerhard; Arrese-Igor, S.; Alegria, A.; Rodriquez-Roa, E; Schurtenberger, P. LU and Dhont, J. K G (2016) In Soft Matter 12(48). p.9705-9727
Abstract

The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization... (More)

The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization effects, experimental spectra on PNIPAM-co-AA [poly(N-isopropylacrylamide-co-acrylic acid)] ionic microgel particles suspended in de-ionized water exhibit three well-separated relaxation modes, which are due to the polarization of the mobile charges within the microgel particles, the diffuse double layer around the particles, and the polymer backbone. Expressions for the full frequency dependence of the electrode-polarization contribution to the measured dielectric response are derived, and a theory is proposed for the polarization resulting from the mobile charges within the microgel. Relaxation of the diffuse double layer is modeled within the realm of a cell model. The net charge and the size of the microgel particles are found to be strongly varying with concentration. A very small value of the diffusion coefficient of ions within the microgel is found, due to a large degree of chemical association of protons to the polymer backbone.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Soft Matter
volume
12
issue
48
pages
23 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85002244053
  • wos:000394087100012
ISSN
1744-683X
DOI
10.1039/C6SM01683A
language
English
LU publication?
yes
id
b4fc1008-b5cf-4c70-9cc1-1c439c2b1768
date added to LUP
2017-02-21 11:15:32
date last changed
2017-09-18 11:33:58
@article{b4fc1008-b5cf-4c70-9cc1-1c439c2b1768,
  abstract     = {<p>The determination of the net charge and size of microgel particles as a function of their concentration, as well as the degree of association of ions to the microgel backbone, has been pursued in earlier studies mainly by scattering and rheology. These methods suffer from contributions due to inter-particle interactions that interfere with the characterization of single-particle properties. Here we introduce dielectric spectroscopy as an alternative experimental method to characterize microgel systems. The advantage of dielectric spectroscopy over other experimental methods is that the polarization due to mobile charges within a microgel particle is only weakly affected by inter-particle interactions. Apart from electrode polarization effects, experimental spectra on PNIPAM-co-AA [poly(N-isopropylacrylamide-co-acrylic acid)] ionic microgel particles suspended in de-ionized water exhibit three well-separated relaxation modes, which are due to the polarization of the mobile charges within the microgel particles, the diffuse double layer around the particles, and the polymer backbone. Expressions for the full frequency dependence of the electrode-polarization contribution to the measured dielectric response are derived, and a theory is proposed for the polarization resulting from the mobile charges within the microgel. Relaxation of the diffuse double layer is modeled within the realm of a cell model. The net charge and the size of the microgel particles are found to be strongly varying with concentration. A very small value of the diffusion coefficient of ions within the microgel is found, due to a large degree of chemical association of protons to the polymer backbone.</p>},
  author       = {Mohanty, P. S. and Nöjd, S. and Bergman, M. J. and Nägele, Gerhard and Arrese-Igor, S. and Alegria, A. and Rodriquez-Roa, E and Schurtenberger, P. and Dhont, J. K G},
  issn         = {1744-683X},
  language     = {eng},
  number       = {48},
  pages        = {9705--9727},
  publisher    = {Royal Society of Chemistry},
  series       = {Soft Matter},
  title        = {Dielectric spectroscopy of ionic microgel suspensions},
  url          = {http://dx.doi.org/10.1039/C6SM01683A},
  volume       = {12},
  year         = {2016},
}